Those look like olive trees? Grasses and agaves -- a drought-tolerant alternative to lawn in hot, dry climates. Oehme Van Sweden drought tolerant demonstration garden with grasses and agave at Cornerstone.
Water-wise gardening doesn't mean you have to plant only natives. There's a huge list of world-wide plants you can use to spectacular effect. For more practical gardening advice, see our feature 75 Gardening Ideas (Page Australian House & Garden, May